Continuous production dielectric heating apparats

ABSTRACT

A movable support, such as a cart or dolly moves along a continuous production line path, preferably in a closed loop. Each cart carries a pair of spaced essentially parallel plates, between which the structure to be heated dielectrically is to be placed. The plates are connected to a non-contacting electric RF energy coupler, such as a pair of spaced coils, between which another coil is movable, the other coil being connected over a movable arm to an RF generator. As the carts move along the path, the arm carrying the coil connected to the generator is engaged by a cart. Its coil matches with the coils carried by the cart, and is moved synchronously therewith for a predetermined period of time during which energy is transferred from the generator to the plates. To provide for uniform voltage distribution on the plates, tuning stubs or lines, preferably with a movable short circuit, are connected to the plates at suitable locations.

Marini Sept. 5, 1972 [54] CONTINUOUS PRODUCTION DIELECTRIC HEATINGAPPARATS [72] Inventor: Aldo M. Marini, Woodbury, N.Y.

[73] Assignee: Willcox& Gibbs, Inc., New York,

22 Filed: Aug. 19,1971

21 Appl. No.: 173,043

[52] US. Cl. ..219/10.8l, 156/380, 219/1061, e 219/1069, 264/22 [51]Int. Cl. ..H05b 9/04 [58] Field of Search..2l9/l0.6l, 10.69, 10.73,10.81; 264/22, 45; 156/272, 380

[56] References Cited UNITED STATES PATENTS 2,504,754 4/1950 Sweeny..l56/272 x 2,548,093 4/1951 Blewitt ..219/10.69 3,475,522 10/1969Garibiar et al ..219/l0.8l x

Primary Examiner-J. V. Truhe Assistant Examinerl-lugh D. JaegerAttorney-Robert D. Flynn et a1.

[57] ABSTRACT A movable support, such as a cart or dolly moves along acontinuous production line path, preferably in a closed loop. Each cartcarries a pair of spaced essentially parallel plates, between which thestructure to be heated dielectrically is to be placed. The plates areconnected to a non-contacting electric RF energy coupler, such as a pairof spaced coils, between which another coil is movable, the other coilbeing connected over a movable arm to an RF generator. As the carts movealong the path, the arm carrying the coil connected to the generator isengaged by a cart. lts coil matches with the coils carried by the cart,and is moved synchronously therewith for a predetermined period of timeduring which energy is transferred from the generator to the plates. Toprovide for uniform voltage distribution on the plates, tuning stubs orlines, preferably with a movable short circuit, are connected to theplates at suitable locations.

20 Claims, 8 Drawing Figures PATENTEDSEP 51912 SHEET '4 (IF 4 -WATERWETTING AGENT MEASURE QUANTITY FIG.8

CONTINUOUS PRODUCTION DIELECTRIC HEATING APPARATS RELATED APPLICATIONSMETHOD OF MANUFACTURING LIGHT- WEIGHT BODIES OF EXPANDED, HEAT SE'I'TA-BLE RESINE, U.S. Ser. No. 173,044 filed Aug. 19,1971

FIELD OF THE INVENTION The present invention relates to a dielectricheating apparatus for use in continuous production of structures ofexpanded polystyrene, or similar material, for example pallets. Duringproduction of such structures, heat has to be generated internallythereof to cure and fuse the expanded polystyrene into a unitary bodyand to fuse the polystyrene to cover sheets or layers, if used.

Co-pending application U.S. Ser. No. 173,044 filed Aug. 19, 1971,entitled METHOD OF MANUFAC- TURING LIGHT-WEIGHT BODIES OF EXPANDED,HEAT-SETTABLE RESIN, assigned to the assignee of the presentapplication, discloses a method of manufacturing such bodies, andparticularly large-area, large-volume light-weight bodies which arestructurally strong, capable of carrying substantial weight, andresistant to mechanical damage, and which can be shaped as desired bybeing molded in a suitable mold. The present invention is directed to anapparatus to efficiently and effectively carry out the method describedin the foregoing application and to do so in one continuous productionprocess, with a minimum of equipment and in which all major componentsof the equipment are practically continuously operating so that theutilization factor of the equipment is high. The disclosure of theaforementioned application is hereby incorporated by reference.

Conventional methods of molding expanded polystyrene, that is,polystyrene which has a gas occluded therein such as butane, pentane,propane, carbon dioxide, FREON or the like depended on molding thematerial between mold forms which were heated by applying steam, orother heat sources thereto. Apparatus to carry out such moldingprocesses applied heat from the outside, that is, closest to the moldsurface. This results in a smooth outer surface, which may be desiredbut the interior may remain rather loose and possibly incompletelyfused. The resulting structures, while useful as packing material forfragile articles, coffee cups, or for heat insulating structures, have,however, low mechanical strength. To fuse large-area, large-volumebodies of heat-settable resin into one unitary whole requires apparatuscapable of producing heat in the inside of the body itself, in spite ofthe fact that the material, itself, has excellent heat insulatingproperties.

It is an object of the present invention to provide an apparatus todielectrically heat large-area structures internally.

' SUBJECT MATTER OF THE PRESENT INVENTION Briefly, movable supports areprovided, for example in the form of carts or dollies, moving along acontinuous production line path, preferably a closed loop. Each cart ordolly includes a pair of spaced, essentially parallel plates, adapted tohave the structure to be heated located therebetween; if the structureis in loose form, such as expanded beads, a mold filled with the beadsis placed between the plates. The plates are ener gized byhigh-frequency energy, as they move along the production path. In apreferred form, the plates are connected to halves of a coil, having acenter gap; a coupling coil is placed in the center gap, the couplingcoil being electrically connected to an RF generator, and mechanicallysupported to move along withthe cart or dolly as it moves along theproduction path for example by mechanically latching on the dolly. Thus,

power can be transferred from the RF generator to the plates on the cartto provide for heating of the material between the plates for asufficient period of time for fusion of the body, for example for asufficiently long period to transform moisture within plastic beads tosteam, the heat from the steam fusing the beads into a unitary body. Theheating effect over the extent of plates should be uniform, and thusuniform voltage distribution is required so that the energy transfer tothe substance between the plates will be uniform. To provide for suchuniform voltage distribution, the plates are tuned by connecting tuningstubs thereto which can be shorted by a suitable shorting stub.

Parallel to a portion of the production path of the carts is a loadingand unloading path having a number of operating stations which operatein synchronism with movement of the carts along the production path. Atthe operating stations, molded articles are removed from the carts orthe molds, if used), and the carts reloaded; if molds are used, themolds are lined, filled with plastic material for example in bead form,with a top cover sheet, and re-introduced between the plates. Thisapparatus, although independent of the production path, operates insynchronism therewith so that as carts are unloaded by removal offinished articles, empty carts are moved to the loading station forsubsequent transport to the heating point at which RF energy can againbe coupled to the plates of the moving loaded cart.

As an illustration of an article to be made, a detailed description willbe given with respect to the manufacture of pallets.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a fragmentary perspective view of a pallet forming an articleto be made by the apparatus of the present invention;

FIG. 2 is a highly schematic, diagrammatic top view of the productionpaths, and the general arrangement of the apparatus;

FIG. 3 is a fragmentary top view, partly schematic, of the apparatus;

FIG. 4 is a partly schematic circuit diagram of the apparatus;

FIG. 5 is an exploded perspective view of a press cart;

FIG. 6 is a side view of a press cart showing a modified couplingarrangement of RF energy;

FIG. 7 is a perspective partly schematic view of the removal, fillingand loading stations forming part of the apparatus; and

FIG. 8 is a schematic view of the apparatus to place expandedpolystyrene beads into a mold.

Referring now to the drawings and first to FIG. 1 which partlyillustrates a pallet. The pallet comprises a top cover sheet 12, forexample of adhesively coated, reinforced paper and bottom liner ll,likewise of reinforced paper, which may be similar to that of the topcover sheet. Facing surfaces of these sheets are adhered together by athermoplastic adhesive. -A polystyrene fill 5, in expanded, fused formis retained between liner 1! and the top cover sheet 12. It is notnecessary that the liner or the top cover sheet completely cover theexpanded fused polystyrene; thus, polystyrene material may be exposed,as seen at 15. The edges of the top cover sheet and of the liner arefused together. The finished pallet will have a flat bearing portion 37fromwhich load supporting projections 25 project downwardly, with spacestherebetween, for example for engagement by the tines of a fork lifttruck.

The apparatus of the present invention provides a continuous productionpath. Movable supports in the form of dollies, carts, or conveyor units35 are moved along a production path 49, in the direction of arrow 49',as seen at FIG. 2. The dollies or carts (FIGS. 5 and 6) run on a surfaceand are carried along by engagement of pins 51 in a chain 50, laid in aU channel along the track 49. Thecarts support a mold press whichincludes a pair of parallel plates 41, 42. One of the plates, in FIG. 6plate 42, is secured to the structure of dolly 35 for example byinsulators 80 and ad jistable screw connections 81. The other plate,plate 41, is supported by an inflatable cushion 63, to which pressurefluid, such as compressed air can be applied over a connection nipple64. A mold 30, (FIG. 7) lined with liner 11, filled with expanded wettedpolystyrene pellets or beads, and covered with a top cover sheet 12 isinserted between press plates 41, 42. To adjust for minor irregularitiesof the press plates, and to accept molds of different sizes, plywoodsheets 39, 40 are preferably placed between press plates 41, 42 and themold 30 proper, as best seen in FIG. 5. These plywood sheets may have athickness of from one-fourth to 1% inches, and also can actas shims sodifferent sizes of molds can be accommodated without having to re-setthe structural attachment of the fixed plate 42, or the support forcushion 63 in the structure of cart 35.

The cart 35 is provided with non-contacting highfrequency energycouplers which project inwardly towards the center X of the loop path.In a preferred form, these couplers are coils 44 (FIGS. 2, 3, 4, 5);they may be capacitative plates 44' (FIG. 6). Mounted at the center X isa swingable arm 52 which carries a matching couplingelement, such as acoil 45, or plates 45 which engage in coupling relationship with thematching coupling members 44 (or 44', respectively) on the cart. Thecoupling 45 (or plates 45) are connected by a transmission line 46 toterminals 47 where the transmission line connects to a high-frequencygenerator 48 supplying high-frequency energy, for example in the rangeof about 27 MHz. A suitable voltage at the plates is about 20,000 V.

Assume that a loaded cart 35, that is, a cart into which a mold 30 hasbeen placed is transported by chain 50 along path 49 (FIG. 2). TheU-channel and leading and trailing pins 51 keep the carts on the givenpath. The cart will be moved through region A. Upon further transport,the cart will reach position B, FIGS.

2, 3. The portion of the path beyond region A is circular with a centerpoint X.

Chain 50 is driven by a motor 65. Frame 52 is normally retained in restposition shown in chain-dotted lines in FIG. 3 by springs 52a andpneumatic checks (not shown). As the cart 35 is moved alongthe path 49,beyond region A to region B, the 'arm 52 will engage the cart 35 over aninterengaging locking mechanism 67 and be moved in synchronism with thecart. Any suitable known releasable latch can be used for exam ple aspring-loaded ball, or a catch engaging a matching detent.Upon'engagement of arm 52 and thecart, and as the cart is moving throughregions B and C (FIG. 2), the generator 48 is controlled to be energizedand to transfer power by the non-contacting coupling 44, 45 to theplates 41, 42. When a terminal position D has been reached, for exampleafter about one-fourth to 1 minute or so travel time, an unlatchingcontroller, for example a cam or the like, placed in path 49, unlatchesarm 52 so that it can swing back to the starting position for couplingwith the coils of a next arriving cart. The return movement efiected byspring 52a and as indicated by arrow 52' (FIG. 3) can be much fasterthan forward movement synchronized with the speed of the cart isindependent therefrom. Energization of the generator 48 andtimingcircuits inconnection therewith is itself controlled by switches58 placed along the track 49. Switches 58 cooperate with suitablyarranged actuators on the carts 35; these switches, since they onlysense the presence of the carts 35 can be of the contacting type, suchas microswitches operated by projecting levers; or they can benon-contacting. Suitable devices are photoelectric sensors in which alight from a stationary switch 58 is projected on a mirror located onthe dolly 35 and reflected on a photo cell, photo transistor or the likeat switch 58; inductive couplings; capacitative couplings; and othersensing arrangements known in the art. Connection from the variousswitches 58 to the generator is schematically indicated by control line68.

The path taken by the carts in region C need not be circular, so long asa path similar to that of coils 44 is followed by coil 45. Thus, the arm52 may reciprocate, that is, move in a linear path parallel to a lineartransport path of the carts 35.

Current from HF generator 48 is supplied to terminals 47, hence totransmission line 46 and over coupling elements 45, 44 to the dolly 35for predetermined periods of time, and at predetermined intensities,depending on the material to be fused, its aging, electricalconductivity, moisture content, size of the mold, and the like.High-frequency energy supplied to plates 41, 42 causes heating of themoisture within the mold, thus raising the temperature internallythereof so that the moisture will turn to steam. This steam can escapethrough holes 38 (FIG. 8) formed in the mold, or between the stillunfused sides of the top covering sheet 12 and liner 11. The amount ofenergy supplied can be controlled manually or automatically. FIG. 4illustrates the electrical arrangement in which a controller controlsboth the power (current, at a given voltage, and time) of connection ofHF generator 48, or of its coupling, as schematically indicated at 60,to the transmission line 46. An instrument, schematically illustrated asa watt meter :62 measures the total power that is the energydistribution over the-area of the.

plates 41, 42 should be as uniform a possible. To provide for suchuniformity, tuning stubs 55, 56, in the form of pipes connected toplates 41, 42 are provided, connectable by movable short circuit stubs57. MOre than one set of tuning stubs 55, 56 may be connected to plates41, 42 (FIG. 4,) to improve the-voltage distribution of the plates bothlaterally, as well as horizontally, with respect to the connection ofthe plates with the coupling element 44 (or 44 respectively). The tuningstubs extend at right angles to the plane of the plates. For ,ease ofalignment of the coupling elements on the carts and on arm 52, a pair ofspaced, interconnected coils 44 (FIG. 4) are preferred, with which asingle loop turn 45, secured to the end of arm 52 can engage. The carts,and the plates 41, 42 thereon are slightly bigger than the articles tobe molded; to make industrial-type pallets, dimensions of about 3 to 4feet square are suitable. The carts must be strong enough to counteracta compressive force, schematically indicated at C-C' (FIG. 5) andexerted by inflatable cushion 63; the size and weight of the carts, andindustrial economyprecludes high-precision guidance of the dollied alongthe path and some allowance must therefore be made for misalignmentbetween the coils 44 and 45. Tuning the individual plates 41, 42 of thedollies, individually, permits slight misalignment of the relativelyengaging I-IF energy coupling elements while still providing foruniformity of the field across the plates. It has been found that tuningthe plates, with the filled mold located therein to a frequency off, byabout 1 MHz with respect to the frequency of the generator improves thevoltage distribution and the plates are accordingly tuned to about 28MHz.

After the applied power has reached a certain level, a timer formingpart of controller '53 keeps the power on for about 5-60 seconds, at anaverage rate .of about 5-20 A times 20,000 V. For a full discussion ofthe parameters of the method to fuse expanded polystyrene, reference ismade to the co-pending crossreferenced application entitled METHOD OFMANUFACTURING LIGHT-WEIGHT BODIES OF EXPANDED HEAT-SETTABLE RESIN, Ser.No. 173,044

Compressed air can be applied at connection 64 at any one of the stagesA to C; in a preferred form, compressive force is applied at station Aand maintained when the cart leaves the position B until the moldedstructure is sufficiently cool so that it will not expand further.

Position B, C and D are preferably enclosed within a shielded,protective enclosure 69 to prevent stray radiation. When power istransferred, an ordinary fluorescent light tube 76 unconnected, andsuspended in the region of position C will light or glow, as anindicator, and as a safety warning. Compressive force is preferablyapplied to compressed air inlet 64 beyond the shielding enclosure, andbeyond the point at which possible radiation hazards may exist.

The path F beyond section E, up to the ejection station G is selected tobe long enough to permit plates 41 42 to cool and the resin to set. Forpallets, the length is chosen to provide a running time of the carts 35from section E to section G of about 6 to 10 minutes.

At the ejection station G, (FIG. 2) or before, air pressure is releasedfrom cushion 63, permitting the plates 41, 42 to separate, for exampleunder spring pressure or by gravity. A hydraulically operated pusher 70,controlled by one of the switches 58 upon sensing of presence of a cart35 moves a plunger between the released plates to eject the mold 30 frombetween the plates and place it in a removal position H. The mold 30(see FIGS. 7 and 8)'is formed with openings 38 therethrough so that thefused pallet can readily be removed by differential air pressure on thepallet. An overhead conveyor 71 (FIG. 2) operating in timed relationwith the pusher and equipped with suction cups 6] is lowered on the topsheet 12 and suction is applied, which will lift the pallet out of mold30, for removal to a suitable inspection, and storage position. Ifdesired, compressed air is applied through openings 38. The conveyor 71is preferably inclined upwardly to carry the finished article away andover other structures in the apparatus.

The mold 30 itself comprises a resin impregnated fiberglass body with awooden support structure, capable of running on slides, or conveyortracks 72 in a parallel, shunt path, to be re-filled and for subsequentre-loading in the same, or a different cart 35 at a loading station L.

After having been cleared of the finished pallet, the mold 30 is movedto a fill station 1 (FIGS. 2, 8), where expanded wetted polystyrenebeads or pellets are introduced therein.

Referring to FIG. 8, polystyrene beads which have gas occluded therein,are introduced into a hopper 20 stored in a storage bin'20a, thenexpanded by the addition of steam at a steam injection device 21 andtransported to a storage container 22, where they are stored upwardlyfrom 2 hours, preferably about 5 to 40 hours. The expanded beads are'transported to a measuring station 18 where a measured amount of pelletsare segregated and introduced to an injector 23, where a measured amountof water and wetting agent, mixed together in a mixer 24, are addedthereto, and then conducted to a container 26 in which a stirrer 27 isplaced. Container 26 hasfill guns 34 attached thereto, and includes acontrol element which permits the beads to flow through the filltherethrough, when a mold 30 is located therebeneath, transported, forexample, by an air blast from compressed air tubes 34a. Empty mold 30,located at injection station I has the liner sheet 11 placed thereoverwhich is, in this form, a flat sheet of reinforced paper having diagonalcuts formed therein. A forming plate 32 is lowered on the liner sheet,and resiliently loaded fingers 33, projecting therethrough, fold theliner 11 between the diagonal cuts into depression 31 formed in themold. The liner 11 may also be pro-formed, or pre-folded. The bottom ofthe depression 31 of the mold has small holes 38 therein to permit airto enter from the bottom of the mold, the holes being small enough sobeads cannot fall therethrough.

.A fill plate 29 with spacers 28 thereon, together with beneath a doctorblade 73 or the like, to remove excess peaks of beads. Excess beads areplaced in a collection shoe l9 and reintroduced into distributioncontainer 26. Top cover 12 is applied at station J (FIG. 2) and thelined filled and covered mold 30 is conveyed past an inspection stationK to loading station L to be again introduced between the open plates41, 42 of a cart 35 being transported past the loading station I...

The movement of the molds 30 over the shunt path' from station G tostation L is synchronzied with move- I ment of the carts 35. The timetaken to unload the mold at station E, and line, fill, cover, andinspect the mold at stations I to K will match the travel time of a cartfrom station G to station L, or be a multiple thereof so that, when aloaded mold is ready for loading at station L, an empty cart will bepresent thereat.

I claim 1. Continuous production dielectric heating apparatus forstructures of expanded resin comprising a movable support, means forminga continuous production line path, and means for moving said supportalong said continuous production line path;

a pair of spaced, essentially parallel plates on said support adapted tohave the structure located therebetween;

an RF generator having an output coupling;

a non-contacting electric RF energy coupling means coupling the RFgenerator to said plates including a first non-contacting couplingelement secured and connected to said plates and a transmission linehaving one end thereof coupled to the output coupling of the RFgenerator and having, at the other end, a movable terminal and a secondnoncontacting coupling element matching, and capable of electricallycoupling for power transfer with said first non-contacting couplingelement;

means moving said other end of the transmission line and said firstcoupling element into non-contacting RF energy transfer couplingengagement and moving said coupling means of the RF generator and ofsaid spaced plates in synchronism, for a predetermined time period,during movement of said support along its production line path;

means energizing said RF generator during at least a portion of the timesaid coupling means are in energy-transmitting coupling relation; and

tuning means connected to each of said plates and tuning said plates foruniform voltage distribution over the area of said plates when thestructure is located between said plates.

2. Apparatus according to claim 1, wherein said movable support meanscomprises a plurality of similar conveyor units travelling in a closedloop path having a portion comprising an essentially circular path, thetransmission line 8 being pivoted at the center of the circular portion.

3. Apparatus according to claim 1, wherein said movable support meanscomprises a plurality of similar conveyor units travelling in a closedloop path;

each of said conveyor units comprising means holding said parallelplates in spaced relation to provide an intermediate space for insertiontherebetween of a mold to contain material which is to be dielectricallyheated to form the structure;

path

and means moving said plates towards each other, 7

under pressure.

4. Apparatus according to claim 1, wherein said noncontacting couplingmeans coupling said plates and said RF generator comprises interengagingcoupling loops.

5. Apparatus according to claim 4, wherein one of said coupling loopscomprises a plurality of groups of interconnected conductors forming onecoupling element, said groups of conductors being spaced from each otherby a gap;

and the other of said coupling loops comprises at least one loop portionforming the other coupling element and fitting within said gap to permitrelative movement, as well as engagement and disengagement of couplingof said loops.

6. Apparatus according to claim 1, wherein said noncontacting couplingmeans coupling said plates and said RF generator together comprisesinterengaging plates to provide for capacitative coupling.

7. Apparatus according to claim 1, wherein said tuning means includestuning stubs connected to said plates and a movable short circuit stubinterconnecting the tuning stubs.

8. Apparatus according to claim 7, wherein said tuning stubs comprise atleast one tuning stub array having conductors extending at right angleswith respect to the plane of said plates.

9. Apparatus according to claim 1, including means shielding said RFgenerating means, said transmission line, and said movable support atleast when said movable support is located such that the coupling meansare in coupling engagement, to reduce stray radiation.

10. Apparatus according to claim 1, wherein the means moving said otherend of the transmission line in synchronism with the firstnon-contacting coupling element comprises latching means engaging themovable support and the transmission line.

11. Apparatus according to claim 1, in combination with a mold elementof low-dielectric loss material inserted between said plates, said moldelement being lined with a liner having a thermoplastic adhesivecoating, and filled with wetted expanded thermoplastic and forsubsequent cooling of said material in said mold for a period of about6-l0 minutes.

13. Apparatus according to claim 12, including an unloading and loadingstation along the closed loop, and located in advance of that portion ofthe path at which said coupling means can engage in coupling engagement;

said loading and unloading station including means cooperating with saidmovable plates to permit removal of said mold at the unloading station,insertion of a newly filled mold at the loading station and closing ofsaid plates, towards each other and on the mold, under pressure.

14. Apparatus according to claim 13, wherein the loading and unloadingstation comprises means removing the mold from between the plates andexposing the finished structure for removal therefrom from the mold;

means forming a filling station for insertion of a liner into the moldand filling the mold with expanded polystyrene beads;

means forming a closing station for placing a top cover sheet over thefilled, lined mold;

and means introducing said filled, lined, covered mold between saidplates.

15. Apparatus according to claim 14, wherein the means removing thestructure from the mold comprises differential air pressure means actingon the structure.

16. Apparatus according to claim 15, wherein the differential pressuremeans are vacuum cups;

first conveyor means are provided carrying the vacuum cups and liftingthe structure from the mold and transporting said structure away fromsaid loading-unloading station;

and second transport means are provided acting on the empty mold andguiding said emptymold, in sequence, in alignment with said fillingstation, said closing station and said means -to introduce said filled,lined mold between said plates.

17. Apparatus according to claim 1, including positioning switcheslocated along the production line path and controlling the applicationof power from the RF generator to the energy coupling means.

18. Apparatus according to claim 11, wherein the production path alongwhich the conveyor is movable is a continuous loop line;

and the path along which the mold is guided by said transport meanscomprises a shunt path extending for a fraction of the length of saidloop line along said production line path.

19. Apparatus according to claim 1, including motor means moving saidmovable supports along said production line path at a predeterminedspeed;

the speed of the support, and the movement of the mold through saidshunt path being synchronized for timed removal of the filled mold fromthe conveyor, lining the empty mold, filling the mold and covering ofthe mold, and reintroducing the mold into a conveyor moving along saidpath.

20. Apparatus according to claim 1, wherein the structures are pallets,having a load bearing surface portion and projecting portions;

and the movable support means comprises dollies having said platesmounted thereon, the plates being slightly larger than the surfaceportion of the p le and t e tuning means comprises tuning stubsconnected to said plates, and a movable short circuit stubinterconnecting the tuning stubs.

1. Continuous production dielectric heating apparatus for structures ofexpanded resin comprising a movable support, means forming a continuousproduction line path, and means for moving said support along saidcontinuous production line path; a pair of spaced, essentially parallelplates on said support adapted to have the structure locatedtherebetween; an RF generator having an output coupling; anon-contacting electric RF energy coupling means coupling the RFgenerator to said plates including a first non-contacting couplingelement secured and connected to said plates and a transmission linehaving one end thereof coupled to the output coupling of the RFgenerator and having, at the other end, a movable terminal and a secondnon-contacting coupling element matching, and capable of electricallycoupling for power transfer with said first non-contacting couplingelement; means moving said other end of the transmission line and saidfirst coupling element into non-contacting RF energy transfer couplingengagement and moving said coupLing means of the RF generator and ofsaid spaced plates in synchronism, for a predetermined time period,during movement of said support along its production line path; meansenergizing said RF generator during at least a portion of the time saidcoupling means are in energy-transmitting coupling relation; and tuningmeans connected to each of said plates and tuning said plates foruniform voltage distribution over the area of said plates when thestructure is located between said plates.
 2. Apparatus according toclaim 1, wherein said movable support means comprises a plurality ofsimilar conveyor units travelling in a closed loop path having a portioncomprising an essentially circular path, the transmission line beingpivoted at the center of the circular path portion.
 3. Apparatusaccording to claim 1, wherein said movable support means comprises aplurality of similar conveyor units travelling in a closed loop path;each of said conveyor units comprising means holding said parallelplates in spaced relation to provide an intermediate space for insertiontherebetween of a mold to contain material which is to be dielectricallyheated to form the structure; and means moving said plates towards eachother, under pressure.
 4. Apparatus according to claim 1, wherein saidnon-contacting coupling means coupling said plates and said RF generatorcomprises interengaging coupling loops.
 5. Apparatus according to claim4, wherein one of said coupling loops comprises a plurality of groups ofinterconnected conductors forming one coupling element, said groups ofconductors being spaced from each other by a gap; and the other of saidcoupling loops comprises at least one loop portion forming the othercoupling element and fitting within said gap to permit relativemovement, as well as engagement and disengagement of coupling of saidloops.
 6. Apparatus according to claim 1, wherein said non-contactingcoupling means coupling said plates and said RF generator togethercomprises interengaging plates to provide for capacitative coupling. 7.Apparatus according to claim 1, wherein said tuning means includestuning stubs connected to said plates and a movable short circuit stubinterconnecting the tuning stubs.
 8. Apparatus according to claim 7,wherein said tuning stubs comprise at least one tuning stub array havingconductors extending at right angles with respect to the plane of saidplates.
 9. Apparatus according to claim 1, including means shieldingsaid RF generating means, said transmission line, and said movablesupport at least when said movable support is located such that thecoupling means are in coupling engagement, to reduce stray radiation.10. Apparatus according to claim 1, wherein the means moving said otherend of the transmission line in synchronism with the firstnon-contacting coupling element comprises latching means engaging themovable support and the transmission line.
 11. Apparatus according toclaim 1, in combination with a mold element of low-dielectric lossmaterial inserted between said plates, said mold element being linedwith a liner having a thermoplastic adhesive coating, and filled withwetted expanded thermoplastic material.
 12. Apparatus according to claim11, wherein said movable support means comprises a plurality of similarconveyor units, and said production line path is a closed loop; and thespeed of said conveyor units along said closed loop, with respect to thelength of the path is adjusted to provide a time duration ofapproximately 8-60 seconds for interengagement of the elements of thecoupling means to provide for heating, and setting of said thermoplasticmaterial in said mold; and for subsequent cooling of said material insaid mold for a period of about 6-10 minutes.
 13. Apparatus according toclaim 12, including an unloading and loading station along the closedloop, and located in advance of that portion of the path at which saidCoupling means can engage in coupling engagement; said loading andunloading station including means cooperating with said movable platesto permit removal of said mold at the unloading station, insertion of anewly filled mold at the loading station and closing of said plates,towards each other and on the mold, under pressure.
 14. Apparatusaccording to claim 13, wherein the loading and unloading stationcomprises means removing the mold from between the plates and exposingthe finished structure for removal therefrom from the mold; meansforming a filling station for insertion of a liner into the mold andfilling the mold with expanded polystyrene beads; means forming aclosing station for placing a top cover sheet over the filled, linedmold; and means introducing said filled, lined, covered mold betweensaid plates.
 15. Apparatus according to claim 14, wherein the meansremoving the structure from the mold comprises differential air pressuremeans acting on the structure.
 16. Apparatus according to claim 15,wherein the differential pressure means are vacuum cups; first conveyormeans are provided carrying the vacuum cups and lifting the structurefrom the mold and transporting said structure away from saidloading-unloading station; and second transport means are providedacting on the empty mold and guiding said empty mold, in sequence, inalignment with said filling station, said closing station and said meansto introduce said filled, lined mold between said plates.
 17. Apparatusaccording to claim 1, including positioning switches located along theproduction line path and controlling the application of power from theRF generator to the energy coupling means.
 18. Apparatus according toclaim 11, wherein the production path along which the conveyor ismovable is a continuous loop line; and the path along which the mold isguided by said transport means comprises a shunt path extending for afraction of the length of said loop line along said production linepath.
 19. Apparatus according to claim 1, including motor means movingsaid movable supports along said production line path at a predeterminedspeed; the speed of the support, and the movement of the mold throughsaid shunt path being synchronized for timed removal of the filled moldfrom the conveyor, lining the empty mold, filling the mold and coveringof the mold, and reintroducing the mold into a conveyor moving alongsaid path.
 20. Apparatus according to claim 1, wherein the structuresare pallets, having a load bearing surface portion and projectingportions; and the movable support means comprises dollies having saidplates mounted thereon, the plates being slightly larger than thesurface portion of the pallet; and the tuning means comprises tuningstubs connected to said plates, and a movable short circuit stubinterconnecting the tuning stubs.